The present invention provides a light-weight fiber-reinforced composite material that has excellent flame retardance and mechanical properties and never emits a halogen gas. The present invention also provides a prepreg and en epoxy resin composition suited to obtain the above described fiber-reinforced composite material. The present invention also provides an integrated molding which is produced using the above described fiber-reinforced composite material, thereby suitable for use in electric/electronic casings. The epoxy resin composition is such that it contains the following components [A], [B] and [C]: [A] epoxy resin, [B] amine curing agent, and [C] phosphorus compound, wherein the concentration of the component [C] is 0.2 to 15% by weight in terms of phosphorus atom concentration.